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NISTIR 6962The Virtual Cement and Concrete TestingLaboratory Consortium.Annual Report 2002Editor: Jeffrey W. Bullard1.

NISTIR 6962The Virtual Cement and ConcreteTesting Laboratory ConsortiumAnnual Report 2002Editor: Jeffrey W. BullardBuilding and Fire Research LaboratoryJanuary 2003U.S. DEPARTMENT OF COMMERCEDonald L. Evans, SecretaryTECHNOLOGY ADMINISTRATIONPhillip J. Bond, Under Secretary of Commerce for TechnologyNATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGYArden L. Bement, Jr., Director

ContentsContents .iiiVirtual Cement and Concrete Testing Laboratory Consortium.1VCCTL Technical Notes and Software Notes.4VCCTL Publicity.6VCCTL Consortium Members.7Materials Characterization .8Hydration Research .13Rheological Properties .16Elastic Properties .21Durability Research.24Case Study I .28Case Study II .30Case Study III .32NIST/Industry VCCTL Funding .34NIST Equipment and Facilities .35For More Information .39iii

.Virtual Cement andConcrete TestingLaboratory ConsortiumAnnual Report 2002BackgroundThe Virtual Cement and Concrete Testing Laboratory (VCCTL) Consortium was formed inJanuary 2001. Headquartered in the Building and Fire Research Laboratory (BFRL) at theNational Institute of Standards and Technology (NIST), the consortium originally consistedof three NIST laboratories: BFRL, the Information Technology Laboratory (ITL), and theMaterials Science and Engineering Laboratory (MSEL), and six industrial members: Cemex,Dyckerhoff AG, Holcim Inc., Master Builders Technologies (MBT), the PortlandCement Association (PCA), and W.R. Grace & Co.- Conn. The overall goals of theconsortium were—and continue to be—to develop a virtual testing system that will reduce theamount of physical concrete testing needed and expedite the research and developmentprocess. This will result in substantial time and cost savings to the concrete constructionindustry as a whole.The VCCTL Consortium Oversight Board, consisting of one representative from eachmember organization and the VCCTL Consortium Manager from NIST, governs the activitiesand direction of the consortium. The oversight board meets twice each year to reviewresearch progress and set the scope and agenda of future research. Within each industrialparticipant’s laboratory, one researcher is assigned to participate in the research programs ofthe consortium. Once per year, the most recent version of the VCCTL system software isinstalled on a Linux-based PC1 at each participating member’s laboratory.The ultimate goal of the consortium is to address durability and service life prediction, but themembers recognized that first efforts must be concentrated towards enhancing the currentmicrostructure models and property calculations. Therefore, the three major initial researchtopics of the consortium were: 1) enhancements to the cement hydration and microstructuredevelopment model to consider additional supplementary materials such as slags andlimestones and the prediction of pore solution concentrations, 2) computation of the elasticproperties (elastic modulus, creep, shrinkage) of three-dimensional microstructures,1Commercial equipment, instruments, and materials mentioned in this report are identified to fosterunderstanding. Such identification does not imply recommendation or endorsement by the NationalInstitute of Standards and Technology (NIST), nor does it imply that the materials or equipmentidentified are necessarily the best available for the purpose.1

and 3) experimental measurement and computer modeling of the rheological properties(viscosity, yield stress) of cement-based materials.This document reports the activities of the VCCTL Consortium in 2002.Overview of Activities in 2002The 2002 calendar year represents the second year (hereafter called Year 2) of the initialthree-year consortium term. Year 2 witnessed significant growth in the membership of theconsortium. Sponsored research expanded into new areas, while existing topics ofinvestigation were further refined in response to major progress in research.Three new members were welcomed into the VCCTL Consortium in Year 2: The International Center for Aggregates Research (ICAR), Austin, Texas, USA Verein Deutscher Zementwerke eV (VDZ), Düsseldorf, GERMANY Sika Technology AG, Zürich, SWITZERLAND (effective January 2003)In addition, two other organizations have expressed interest in joining the consortium and areexpected to become members in Year 3: Association Technique de l’Industrie des Liants Hydrauliques (ATILH), Paris,FRANCE National Ready Mix Concrete Association (NRMCA), Silver Spring, MD, USAWith these new and prospective members, the VCCTL Consortium is well represented bymajor research and service organizations, by every major constituent of concrete—cement,aggregate, and chemical admixtures, and by the major manufacturers of concrete.One of our industry partners, Degussa Construction Chemicals/MBT, underwent majororganizational changes throughout 2002. An unfortunate consequence of these changes wastheir decision to discontinue their participation in the VCCTL Consortium for the present. Asa chemical admixture supplier, MBT was one of our more active participants over the pasttwo years. Their VCCTL representative, Dr. Davide Zampini, was instrumental in modifyingthe CEMHYD3D hydration model to allow deactivation of clinker surfaces. The consortiumwill miss the contributions of MBT, and of Dr. Zampini in particular, and we sincerely hopethat they would choose to renew their participation in the future.Year 2 was also marked by major strides in research, which built upon the momentumestablished in the first year [1]. Collaborative investigations between NIST researchers andthe industry members led to better understanding and improved computer models in severalareas of research, as summarized in the table on the following page.2

gyDurabilityCalibration of PSD measurements, aggregate shape and sizeanalysis/databaseTracking pore solution composition, model for dependence ofhydration kinetics on pH, influence of alkali salts on hydrationElastic moduli at early agesCross-calibration of rheometers, simulation of rheometer flows,simulation of suspensions with real aggregate shapesSulfate attack models and databaseConsiderable effort was placed on upgrading and enhancing the user interface to the VCCTLmodels. The flexibility and portability of a web-based interface was retained while at thesame time adding considerable automation of data entry tasks that previously required tediousand time-consuming typing. The VCCTL User’s Guide that accompanies the software hasbeen completely updated, and the web forms in Version 3.0 are now extensively linked to theUser’s Guide to provide context-specific help for virtually every entry of every form. Userswill also notice a new “look and feel” to the interface, some of which will be evident in thisreport.Note that each of the major research sections in this report begin with a quote. Several ofthese quotes were taken from Hal Taylor’s famous book, Cement Chemistry [2], to pay tributeto this great cement scientist who passed away in 2002.References[1] “The Virtual Cement and Concrete Testing Laboratory Consortium Annual Report 2001,”NISTIR 6840, U.S. Department of Commerce. Edited by D.P. Bentz, December 2001.[2] H.F.W. Taylor, Cement Chemistry. 2nd Edition. Thomas Telford Publishing, London,1997.3

VCCTL Technical Notesand Software NotesTechnical Notes Technical Note VCCTL-01: Estimation of the Degree of Hydration of Portland Cementby Determination of the Non-Evaporable Water Content Technical Note VCCTL-02: SEM/X-ray Imaging of Cement Powders Technical Note VCCTL-03: Quantitative Determination of Calciumsulfate Dihydrateand Calciumsulfate Hemihydrate in Cement by Means of Thermogravimetric Analysis(from Dyckerhoff) Technical Note VCCTL-04: Estimation of the Degree of Hydration of Cement byMeasurement of Chemical Shrinkage Technical Note VCCTL-05: Measuring the Viscosity of Cement Paste and Mortar (duein 2003) Technical Note VCCTL-06: Standard Method for Measuring the Particle SizeDistribution of Cement (due in 2003) Technical Note VCCTL-07: Wet/Dry Cycling Method for Determining Resistance toSulfate Attack (due in 2003)Software Notes Software Note VCCTL-01: CONCRETEVIEW software Software Note VCCTL-02: Software for Hydration/Drying of 2-mm ThickMicrostructures Software Note VCCTL-03: Computation of Cement Paste Elastic Properties4

Manuals D.P. Bentz and G.P. Forney, “User’s Guide to the NIST Virtual Cement and ConcreteTesting Laboratory. Version 1.0”. NISTIR 6583. U.S. Department of Commerce,November 2000. J.W. Bullard, “User’s Guide to the NIST Virtual Cement and Concrete TestingLaboratory. Version 3.0” to be published in early 2003.Reports “The Virtual Cement and Concrete Testing Laboratory Consortium Annual Report2001”. Edited by D.P. Bentz. NISTIR 6840. U.S. Department of Commerce, December2001.5

VCCTL PublicityNEW2002Presentation to the ACI Strategic Development Council as part of the New TechnologyShowcase, Orlando, FL (November 18, 2002). “VCCTL: A Web-Based Virtual Cementand Concrete Testing Laboratory.”NEW2002Special presentation by E.J. Garboczi to the Research Committee of the National ReadyMixed Concrete Association, Arlington, VA (October 6, 2002). “VCCTL: A Web-BasedVirtual Cement and Concrete Testing Laboratory.”NEW2002Special 90-minute presentation by J.W. Bullard and E.J. Garboczi at the PortlandCement Association meeting, Chicago, IL (September 16, 2002). “VCCTL: A WebBased Virtual Cement and Concrete Testing Laboratory.”NEW2002Daily Commercial News and Construction Record (September 13, 2002). “FacilityProvides Virtual Testing for Concrete.”NEW2002Special symposium organized by G.J. Frohnsdorff and C. Ferraris, presented to ASTMCommittees C-01 and C-09, Salt Lake City, UT (June 26, 2002). “The Virtual Cementand Concrete Testing Laboratory.” Concrete Construction (November, 2001). “Virtual Concrete Laboratory”The Concrete Producer (October, 2001). “E-Concrete: Let's Try a Little Left Thinking”Government Computer News (August 27, 2001). “NIST Team Sees in Stereo” (available athttp://www.gcn.com/20 25/news/16941-1.html)Engineering News Record (June 25, 2001). “Website Aims to Cut Concrete Analysis”(available at http://www.enr.com/itnews/it62501e.asp )Civil Engineering (June, 2001). “Virtual Concrete Lab Saves Time, Reduces Material Cost”NIST Technology at a Glance (Spring, 2001). “Co-Op Corner, Virtual Cement Laboratory”NIST Update (February 20, 2001). “Virtual Lab Consortium to Test Concrete and CementFormulas”Concrete Technology Today- PCA (December, 2000). “ The Future of Materials Testing?Virtual Testing of Concrete Will Save Time and Money”VCCTL Newsletter. In Year 2, NIST began publishing a quarterly VCCTL Newsletter,which is distributed to members of the VCCTL Consortium and to users who login to thepublic domain site for the VCCTL software (Version 1.0). The newsletter highlightsapplications by users of the public domain version and also gives periodic tips for using thesoftware. The VCCTL Newsletter is intended as a source of useful information as well as apublicity tool for the consortium.6

VCCTL Consortium MembersNISTHolcim, Inc.Dr. Weiping MaDr. Jeffrey W. Bullard (BFRL)Dr. Judith Devaney (ITL)Dr. Chiara F. Ferraris (BFRL)Dr. Glenn P. Forney (BFRL)Dr. Edward J. Garboczi (BFRL)Dr. Vincent A. Hackley (MSEL)Mr. John Hagedorn (ITL)Mr. Peter Ketcham (ITL)Dr. Nicos S. Martys (BFRL)Mr. Steve Satterfield (ITL)Mr. Paul Stutzman (BFRL)Mr. John Winpigler (BFRL)Portland Cement AssociationDr. Paul TennisW.R. Grace & Co.- Conn.Dr. Vijay GuptaDr. David MyersCemex TrademarksWorldwide, LtdDyckerhoff AGDr. Claus-Jochen HaeckerMr. Juan CharqueroMs. Karen OrnelasMr. Javier VazquezVerein DeutscherZementwerke eV (VDZ)Association Technique de l’Industrie desLiants Hydrauliques (ATILH)Dr. Alain CapmasProf. Denis Damidot (Mines de Douai)Dr. Martin SchneiderDr. Georg LocherDr. Maria Teresa AlonsoSika Technology AGInternational Center for AggregatesResearch (ICAR)Dr. Robert FlattProf. David W. Fowler (U. Texas at Austin)7

Materials CharacterizationThere is an underlying philosophy [in] the branch of engineering known as“materials science”: To understand the properties (i.e. observablecharacteristics) of engineering materials, it is necessary to understand theirstructure on the atomic and/or microscopic scale. [1].BackgroundWithout meticulous characterization of the starting materials, it is practically impossible toformulate fundamental microstructure models of the hydration and properties of a cementpaste, mortar, or concrete. One of the signature features and strengths of the CEMHYD3Dhydration model is its incorporation of microstructural information with unprecedented levelsof detail.Proper characterization of cement-based materials is not a trivial task. The starting powderstypically consist of a wide distribution of particle sizes, each particle of which is composed ofmultiple phases with variable chemical compositions. Many products of hydration areamorphous or poorly crystalline, and these may be finely intermixed. An additionalcomplication is that some microstructural characteristics have not been rigorously defined. Insome cases it has not been possible even to properly calibrate measurements, like those ofparticle size distribution (PSD), because of the absence of an accepted reference material orstandard methodology.Recognizing the critical importance of materials characterization for predictions ofmicrostructure development, physical properties, and durability, the consortium hascontinually sought to achieve greater accuracy and detail in these types of measurements, andto supply robust, calibrated measurement techniques where those have been lacking.Activities in Year 1Particle Size Distribution. In collaboration with ASTM Subcommittee C01.25, it wasestablished that there is no standard test for measuring the PSDs of cements. NIST obtaineddata generated by an ASTM-sponsored round-robin test in 2000. NIST used these data toinitiate an analysis of the type of techniques that are used most commonly, and to develop amethod for determining a statistically valid mean PSD from the distributions generated bymultiple laboratories. A small VCCTL round-robin test also helped determine a logicalcourse of action: 1) establish a reference material, and 2) determine which parameters need tobe controlled using the laser diffraction technique (wet or dry).SEM/X-ray Imaging. NIST has pioneered the use of SEM/X-ray imaging for thequantitative characterization of cement powders [2]. This analysis produces a 2-D image ofthe cement powder in which each pixel is identified as one of the major phases of portlandcement, as shown in Figure 1.8

icaCAS2100 µmFigure 1: Processed 2-D image of CCRL Cement 140.Research in Year 2Particle Size Distribution. At the May 2002 meeting of the VCCTL Consortium, it wasagreed that to improve measurements of cement particle size distribution, it is neccesary todevelop a method for separating the individual PSDs of clinker and gypsum phases ininterground cements. Initial efforts focused on physically separating gypsum from clinker ininterblended or interground cements, by selectively sedimenting the powder in a liquid havinga density between the average densities of gypsum and clinker phases. However, this methodwas unsuccessful, probably due to some degree of interphase particle agglomeration.Common methods to deflocculate a powder suspension, such as the use of a chemicaldispersant and ultrasonic agitation, were investigated but also were unsuccessful. A morepromising method may be to use a laser scattering technique to measure the particle sizedistribution of a cement that has been suspended in a liquid, the refractive index of which isaccurately matched to that of the calcium sulfate phase(s). The close matching of refractiveindices could effectively eliminate the gypsum particles as scattering centers, thus allowingthe measurement technique to sample only the clinker particles. Preliminary results of thismethod indicate that benzyl alcohol/ethanol mixtures can be designed to closely match theaverage refractive index of gypsum.With the recognition that a standard method for measuring PSD does not exist, the consortiumtook the lead in trying to establish such a standard. Working through ASTM SubcommitteeC01.25, Dr. Ferraris (NIST) prepared two reports analyzing two ASTM round-robin tests[3,4]. The first round-robin was organized by ASTM and included data from 21 participants.Because no information was gathered during this round-robin about how the measurementswere made (only the generic method was stated ) it was deemed insufficient to establish astandard method or a reference material. Nevertheless, it helped develop the methodology toanalyze the data. The second round-robin was planned by NIST in collaboration with ASTMand included laboratory members of the proficiency program from the Cement and ConcreteReference Laboratory (CCRL) as well as VCCTL members. There were 41 participants inthis round-robin. As data were collected on the parameters used to prepare the specimens andto analyze them, it was used to define a reference material and some basic understanding ofthe standard method. Reference material SRM-114p, distributed by NIST and used for Blainecalibration, was selected. The PSD established in the second round-robin will be included inthe SRM-114p certificate in early 2003. The reference material would be used to “calibrate”an instrument or to validate the procedure used in a laboratory. It was also established thatmost (93 %) of the cement laboratories use a laser diffraction technique, with either liquid9

suspension or aerosol handling of the cement powder. Therefore, NIST agreed to develop astandard procedure to be submitted to ASTM in Year 3, based on laser diffraction.Aggregate Shapes. Ed Garboczi (NIST) began a joint project with ICAR tomathematically represent and analyze aggregate shapes. The project encompasses (1)developing ways to experimentally capture thethree-dimensional images of aggregate assemblies,using X-ray computed tomography, (2) usingimage analysis to isolate individual aggregatepieces from the data, and (3) creating and storing amathematical description of the aggregate shapeusing spherical harmonic expansion [3]. Severaltrials were made to validate the general procedure,and an assessment was made of the convergence ofthe spherical harmonic expansion. Figure 2 showsa comparison of the spherical-harmonic expansionof the initial data for a single rock particle.Figure 2: (Top) Photograph of astreambed rock (volume 5x104 mm3).(Bottom) Spherical harmonic expansion,using 300 terms, of a computedtomography (CT) scan of the same rock.The ultimate objective of this project is to providea database of aggregate shapes for accuratelymodeling the macrostructure of concrete. Askeletal database of shapes will be included inVersion 3.0 of the VCCTL software. Ongoingwork is focusing on analyzing different types ofaggregate (e.g. riverbed vs. crushed) for commoncharacteristics and on enhancing the database.Case Study II in this report provides additionaldetail and validation of the spherical harmonicanalysis of several rock samples by comparing thepredicted volume of each to the true volumemeasured by immersion in a liquid.SEM/X-ray Imaging. Much of the microstructural characteristics of cements are obtained bysegmenting a series of 2-D SEM images into constituent phases, with the aid of X-ray mapsfor the relevant elements. Segmentation is accomplished pixel-by-pixel, using an algorithmthat steps through a decision tree based on the intensity of the X-ray signal for each element ata particular location. In Year 2, the decision tree was expanded to include slag-like materialand a calcium aluminosilicate compound as possible additional phases, as shown in Figure 1.In addition, the color scheme for representing phases was changed to more closely match theactual colors of the phases when they are HF-etched and examined by reflected-lightmicroscopy.Although it is fairly routine, the segmentation procedure involves a considerable amount ofuser intervention and somewhat subjective decisions, especially when thresholding theintensities of the signals for each element’s X-ray map. Researchers in the InformationTechnology Laboratory (ITL) at NIST are actively pursuing applications of machine learning,which can be a powerful tool for analysis of complicated images. The SEM segmentationprocedure could be made simpler and more automated if a way could be developed toimplement machine learning. With sufficient testing and documentation, such a segmentationprotocol could be distributed to the VCCTL Consortium members as part of the softwarewithin a year.10

FutureWork in Year 3 will build on the research progress made in 2002, and will include thefollowing research/development activities:Particle Size Distribution Analysis1.Validate refractive index matching to gypsum as a way to isolate the particle sizedistribution of clinker in interground/interblended cements.2.Develop formulations for benzyl alcohol/ethanol mixtures that are index-matchedrespectively to gypsum, hemihydrate, and anhydrite forms of calcium sulfate.3.Create and validate an algorithm for deconvoluting the individual contributions of twoseparate particle size distributions from a mixture in which one of the PSDs is known.4.Complete documentation of reference data for PSD of SRM-114p5.Develop next-generation SRM 114q as a standard reference material for calibratingparticle size analyzers.6.Draft a standard cement PSD measurement method as a VCCTL TechNote and forASTM.Aggregate Shape Characterization1.Refine and optimize procedures of image and mathematical analysis of aggregates (jointwork between NIST and ICAR)2.Extend the project to characterize shapes of cement particles, and incorporate cementparticle shape in CEMHYD3D hydration model.3.Search for more generally available 3D imaging techniques, besides X-ray computedtomography, for use by consortium members.References[1] J.F. Shackelford. p. 11 in Introduction to Materials Science for Engineers. MacmillanPublishing Company. New York, NY (1985).[2] D.P. Bentz, P.E. Stutzman, C.J. Haecker, and S. Remond, “SEM/X-ray Imaging ofCement-Based Materials,” 7th Euroseminar on Microscopy of Building Materials, Delft,The Netherlands, 457-466 (1999). Available online lor.html11

[3] C.F. Ferraris, V.A. Hackley, A.I. Aviles, and C.E. Buchanan, “Analysis of the ASTMRound-Robin Test on Particle Size Distribution of Portland Cement: Phase I”. NISTIR6883. U.S. Department of Commerce, May 2002. Available athttp://ciks.cbt.nist.gov/ monograph/nist6883/nistir6883.htm .[4] C.F. Ferraris, V.A. Hackley, A.I. Aviles, and C.E. Buchanan, “Analysis of the ASTMRound-Robin Test on Particle Size Distribution of Portland Cement: Phase II”. NISTIR6931. U.S. Department of Commerce, December 2002.[5] E.J. Garboczi, “Three-Dimensional Mathematical Analysis of Particle Shape Using XRay Tomography and Spherical Harmonics: Application to Aggregates Used inConcrete,” Cem. Conc. Res. 32 [10], 1621-38 (2002). Available 134.html .12

Hydration ResearchMathematical modelling [of hydration] has the objective of quantifyingknowledge of the hydration process and microstructure of the resulting material thus allowing the effects of changes in inputs or assumptions contained in themodel to be examined [1].BackgroundBecause the physical, chemical, and durability properties of cement and concrete areultimately dependent on their hydrated microstructures and phase composition, amicrostructure-based model of hydration serves as the core of the Virtual Cement andConcrete TestingLaboratory software [2].Particle Sizew/c ratio, gypsum,The 3-D model ofDistributiondegree of flocculationhydration(CEMHYD3D) [3,4] iscurrently recognized asthe most extensive,3D Particlecomplete, and robustMicrostructurecement paste microstructure model in theworld. The general flowof the model may beAutocorrelationsummarized by severalfunctions fromsteps, as shown in Fig. 3.2-D image ofAs hydration executes inactual cementthe model, a series ofoutput files is created tomonitor specificCuring conditions,properties—chemicalthermal condition,shrinkage, heat release,3-D cement withkineticcoefficientssetting, capillary porosityclinker phases, gypsum,percolation, pH, andand s in Year 1During 2001, researchfocused on threesubtopics: 1) modelingand experimentalmeasurements on systemscontaining limestonefillers, 2) development ofPrediction of hydratedmicrostructure plusvarious propertiesFigure 3: Schematic of CEMHYD3D models.13

a framework for incorporating reactions for slag into CEMHYD3D, 3) modeling of the pHand ion concentration of the pore solution during hydration, 4) creation of options inCEMHYD3D for curing under sealed conditions and for specifying the nature of heat transferbetween system and surroundings, and 5) addition of a supplementary model to monitorhydration/drying in 2 mm-thick slabs [5].Research in Year 2Influence of Alkali Species on Hydration. This project was initiated in late 2001 and hasmade substantial progress in Year 2, although several outstanding questions remain. The goalof this project is to link pore solution pH to hydration kinetics and to validate the modelingwith inter-laboratory experiments on different cements with intentional addition of sodiumand potassium salts. Modification of CEMHYD3D was undertaken at NIST to make apreliminary accounting of the acceleration in hydration with increasing pH, in which thedissolution probability of all four clinker phases was made to depend in the same way on pH.Preliminary experiments, also conducted at NIST, revealed several complications, such as theimportance of experimental mixing procedure in establishing a homogeneous distribution ofalkali species, and the possibility of syngenite precipitation in cements with high initialpotassium content. Suitable modifications were made to CEMHYD3D to allow for syngeniteformation, and modifications were also made to experimental mixing procedures to betterhomogenize the alkali species. Concurrent experiments for validation were conducted onthree different cements at NIST, Cemex, and Dyckerhoff during Year 2. The three cementsexamined were CCRL Cement 140 (at NIST), a white cement (at Cemex), and a Type IPortland cement (at Dyckerhoff). The model predictions of degree of hydration closelymatched experimental results for CCRL Cement 140, but were considerably poorer for theother two cements. Specifically, the predicted degree of hydration at later ages (e.g. 28 days)was much higher than the observed degree of hydration. The discrepancy is likely due tounrealistic or incomplete model assumptions, but the possibility of systematic differences inexperimental procedure at the three laboratories cannot yet be discounted. Therefore, aninvestigation of the discrepancies in Year 3 will involve1.repeating the experiments on identical equipment at NIST (to ensure minimalsystematic error due to differences in procedure or equipment calibration),2.repeating at Cemex and Dyckerhoff the experiments using CCRL Cement 140, and3.making a critical reexamination of CEMHYD3D to better account for otherinfluences of alkali species other than pH. This will also involve the incorporation ofmore realistic algorithms for altering the solubility of anhydrous phases.Despite the mixed results of these experiments, Version 3.0 of the VCCTL software willinclude an option in CEMHYD3D to allow pore solution pH to influence hydration rates. AsCEMHYD3D is improved in this respect, upgrades to the model will be distributed to theconsortium members.FutureIn addition to this continuing work on alkali influences, Year 3 will see an effort to furtherrefine CEMHYD3D for predicting hydration behavior of blended cements with slag and/or flyash additions. Limestone reactions will also be further incorporated and validated. These areareas in which the expertise and collaboration of several consortium members, includingCemex, Dyckerhoff, VDZ, and W.R. Grace, will be essential for making rapid progress.14

Specific Goals1.Collect fundamental experimental data on solubility curves of clinker compounds as afunction of pore solution composition/pH.2.Modify CEMHYD3D to allow for possible pH influences on i

Concrete Testing Laboratory Consortium Annual Report 2002 Background The Virtual Cement and Concrete Testing Laboratory (VCCTL) Consortium was formed in January 2001. Headquartered in the Building and Fire Research Laboratory (BFRL) at the National Institute of Standards and Technology (NIST), the consortium originally consisted